Numerous different apparatus for washing garments and fabrics are known. Examples of patents on washing machines include U.S. Pat. No. 1,358,168 to McCutchen, U.S. Pat. No. 1,455,378 to Allen, U.S. Pat. No. 2,357,909 to Ridge, U.S. Pat. No. 2,816,429 to Kurlancheek, and U.S. Pat. No. 3,444,710 to Gaugler. Such apparatus is, in general, adapted to home use with water-based cleaning systems.
Non-aqueous cleaning apparatus, known as "dry cleaning" apparatus, is also known. Dry cleaning employs an organic solvent such as perchloroethylene in place of an aqueous system. Dry cleaning apparatus is not, in general, employed in the home, and is instead situated at a store or central plant. Problems with convention dry-cleaning systems include the toxic nature of the solvents employed.
Carbon dioxide has been suggested as a dry cleaning medium. See, e.g., U.S. Pat. No. 4,012,194 to Maffei. To date, however, a feasible apparatus for carrying out carbon dioxide cleaning has not been provided. One apparatus is described in U.S. Pat. No. 5,467,492 to Chao et al. This apparatus has apparently been supplanted by the apparatus described in U.S. Pat. No. 5,669,251 to Townsend et al. Townsend describes a dry cleaning system having a hydraulically rotated basket that rests on roller bearings. The system is adapted to use with liquid carbon dioxide. Manifolds are disposed between an outer pressure vessel and the basket and have nozzles that produce jets of liquid carbon dioxide that agitate the garments. The basket is said to be rotated by the friction of the garments against the basket walls (column 4, lines 47-48) or by a paddle wheel or turbine (col. 5, lines 8-9). A disadvantage of Townsend is that the basket is supported by roller bearings around the periphery of the basket, which are complex and prevent simple removal of the basket for cleaning, inspection, etc. A further disadvantage is that no practical means of closing and sealing the vessel is disclosed. Since the vessel is pressurized with carbon dioxide, it is critical that any access door be suitably sealed, and it is critical that any loose garments or other materials not inadvertently fall between seal members and leave the door partially unsealed when the vessel is filled with carbon dioxide. A further disadvantage of Townsend is that roller bearings are required between the basket side wall and the side wall of the pressure vessel. Since roller bearings are relatively large, this increases the "dead space" between the side wall of the basket and the side wall of the pressure vessel, which dead space must be filled with liquid that is not operating to clean clothing within the basket.
U.S. Pat. No. 5,267,455 to Dewees et al. describes a dry cleaning system in which carbon dioxide as a cleaning medium is transferred between vessels by means of a second purge gas such as nitrogen. The use of multiple pressurized gases makes the system considerably more complex. The system employs a rotating basket, but a disadvantage is that the basket is rotated by means of a magnet coupling.
Accordingly, there is a continued need for a feasible dry cleaning apparatus that can be used with a carbon dioxide-based cleaning medium.